The importance of image processing is increasing as the camera-equipped mobile telephones and digital cameras become widespread. There are various such image processing including, for example, a process of super-resolution also known as “digital zooming”, an image recognition process of recognizing and focusing on a human face, and augmented reality in which computer-generated graphics images, being virtual objects, are laid over a real image.
These image processing are based on the “appearance” of an object recorded on imaging elements by capturing an image. The appearance of the object is obtained by the imaging elements receiving light from the light source after being reflected at the object surface.
Therefore, light source information is very important in image processing. In other words, it is very effective to obtain light source information and use the information when capturing images and processing images. For example, in Patent Document 1, virtual objects are laid over the real world, wherein the light source environment is measured so as to add the reflection of the illuminated light on the virtual objects and the shadows produced by the virtual objects.
The light source information is useful not only in image processing but also when a cameraman, being a person who captures an image, obtains an image by an imaging device. For example, in Patent Document 2, the light source position is detected, and the information is used to display the front-lighted condition or the backlighted condition to the cameraman, thereby allowing an ordinary person with no special knowledge to easily take, for example, a backlighted (semi-backlighted) portrait effectively utilizing light and shadows.
Patent Document 1: Japanese Laid-Open Patent Publication No. 11-175762
Patent Document 2: Japanese Laid-Open Patent Publication No. 8-160507